Chapter 3 - Bonding and Chemical interactions

what are molecules

combined atoms of elements

what are chemical bonds

attractive forces that hold atoms together

what is the octet rule

an atom tends to bond with other atoms so that it has eight electrons in its outermost shell

what is an incomplete octet

elements that are stable with fewer than 8 electrons, H(2), He(2), Li(2), Be(4), B(6)

what is an expanded octet

any element in period 3 or greater than can hold more than 8 electrons, P(10), S(12), Cl(12)

what are odd number of electrons

any molecule with an odd number of electrons cannot distribute those electrons

what are ionic bonds

one or more electrons from an atom with low IE are transferred to an atom with a high EA

example of ionic bonding

NaCl

what holds ionic bonds together

the resulting electrostatic attraction between the cation and anion

what structure to ionic bonds form

crystal lattice

what is covalent bonding

an electron pair is shared between 2 atoms that gave similar electronegativity

what elements does covalent bonding occur

nonmetals

what is a coordinate covalent bond

both shared electrons are contributed by only one of the atoms

cation

atom that loses an electron

anion

atom that gains an electron

characteristics of ionic bonds

high melting points, dissolve readily in solvents, good conductors in liquid state, form crystal lattice

what is the function of a crystal lattice structure

the attractive forces between oppositely charged ions are maximized and the repulsive force are minimized

how are covalent bonds formed

when the energy required to form ions throughout the complete transfer of electrons is greater than the energy that would be released upon formation of an ionic bond

properties of covalent bonds

can form bonds with more than one atom, can form more than one bond

what is bond order

the number of shared electron pairs between 2 atoms

what is the bond order of single, double, and triple bonds

1, 2, 3

what is bond length

the average distance between 2 nuclei of atoms in a bond

how is bond length dependent on bond order

when bond order increases bond length decreases

what is bond energy

the energy required to break a bond by separating its components into their isolated gaseous states

which bonds have the greatest amount of bond energy

triple

what is polarity

when atoms have a difference in electronegativity and the more negative has a larger share of electron density

what are nonpolar covalent bonds

no separation of charge across the bond

7 common diatomic moleclues

H, N, O, F, Cl, Br, I

what is polar molecule

a molecule that has a separation of positive and negative charges

what is a dipole moment

a vector quantity pointing in the direction of the more polar bond

what is a coordinate covalent bond

both of the shared electrons originate on the same atom

how does a coordinate covalent bond occur

a lone pair attacked another atom with an unhybridized p-orbital

what does a Lewis structure represent

chemical symbol surrounded by dots representing s or p valence electrons

what is formal charge

the difference between the number of electrons assigned to an atom in a Lewis structure and the number of electrons found in the valence shell

formal charge equation

charge = V(normal number of electrons) - nonbonding -1/2bonding

calculate formal charge of N on NH4+

5(normal) - 0 (all involved in bonding) - ½(8)(number of electrons bonding) = +1

what are resonance structures

Lewis structures that demonstrate the same arrangement of atoms but differ in the specific placement of electrons

Practice resonance structures

Practice resonance structures

what is valence shell electron pair repulsion theory (VSEPR)

3D arrangement of atoms surrounding a central atom is determined by the repulsion between bonding and nonbonding electron pairs in the valence shell of the central atom

VSEPR of 2 regions of density

linear, 180

VSEPR of 3 regions of density

trigonal planar, 120

VSEPR of 4 regions of density

tetrahedral, 109.5

VSEPR of 5 regions of density

trigonal bipyramidal, 90, 120, 180

VSEPR of 6 regions of density

octahedral, 90, 180

what is the difference between electronic geometry and molecular geometry

electronic describes spatial arrangement of all electrons while molecular only involved bonding pairs

what is the coordination number

number of atoms that surround and are bonded to an atom

what do Ch4, NH3, and H2O have in common

same electronic geometry, have the same number of electrons bonded to the central

what is the geometry of H2O

bent or angular

what are London Dispersion Forces

a type of van der Waals force that are attractive or repulsive interaction of short lived dipoles

what is the weakest intermolecular interactions

London

what are dipole-dipole interactions

when polar molecules orient themselves so that oppositely charged ends of the dipole are closer to each other

where are dipole-dipole present

solid and liquid

what are H bonds

when H is bonded to N, O, or F and the H atom carries a small amount of density

what occurs in H bonds

the positive H interacts with the partial negative